Abrasive slurry having high dispersion stability and manufacturing method for a substrate

ABSTRACT

To provide an abrasive slurry having high dispersion stability, including: abrasive fine particles made of one or more kinds of oxides; colloidal fine particles made of colloidal oxide with an average particle size smaller than an average particle size of the abrasive fine particles; and a dispersion medium in which the abrasive fine particles and the colloidal fine particles are dispersed, and a manufacturing method for a substrate as an inorganic substrate, including polishing the substrate using the abrasive slurry. An abrasive slurry according to the present invention keeps high dispersion stability for a long time and shows a satisfactory redispersion property, which can eliminate a problem about precipitation/aggregation as much as possible and can be used as a dispersant-free abrasive containing absolutely no organic dispersant. In particular, by using the abrasive slurry, it is possible to manufacture a substrate such as a silicon substrate used in a semiconductor manufacturing process or an aluminum substrate used in an electrostatic chuck manufacturing process through CMP with industrial advantage.

FIELD OF THE INVENTION

The present invention relates to an abrasive slurry having highdispersion stability. In particular, the invention relates to anabrasive slurry suitably applied to chemical mechanical polishing(hereinafter, referred to as CMP), although its application is notparticularly limited thereto. CMP is widely employed for polishing asurface to be polished of photomask blanks, a glass disk, an opticallens, etc., as well as surface-polishing for leveling a substratesurface in a semiconductor manufacturing process or an electrostaticchuck manufacturing process.

Description of the Related Art

A substrate such as a silicon substrate used in a semiconductormanufacturing process or an aluminum substrate used in an electrostaticchuck manufacturing process needs to be leveled at an extremely highprecision, for instance. As a technique of leveling the substratesurface as a surface to be polished, a leveling technique is adopted,with which the substrate surface is leveled at a high precision withoutany damage by CMP that combines mechanical-polishing withchemical-polishing. Abrasive fine particles are used formechanical-polishing and an etchant is used for chemical-polishing.

In general, as an abrasive used in the above leveling technique, slurryis used, which is prepared by dispersing various kinds of abrasive fineparticles into a dispersion medium such as water. Examples of suchabrasive fine particles include: metal oxides such as cerium oxide(CeO₂) and manganese dioxide (MnO₂); silicon oxides (SiO₂) such as aprecipitated silica, a fumed silica, and a colloidal silica; aluminumoxides (Al₂O₃) such as a fumed alumina and a colloidal alumina. Thoseparticles having different sizes (average particle sizes) areappropriately selected according to a type of the substrate to bepolished or a requisite process speed in the leveling technique.

Accordingly, those abrasive fine particles show poor dispersionstability in the dispersion medium depending on their types or sizes. Togive cerium oxide particles as an example, the particles each have arelatively large specific gravity. Thus, when dispersed into thedispersion medium to prepare an abrasive slurry, the cerium oxide fineparticles are uniformly dispersed for a while after the preparation butbegin to separate not long afterward and precipitate, and finallyaggregate together, resulting in the large particle size and wideparticle size distribution. Thus, there arises a problem of theprecipitation/aggregation. As a result, the process speed changes withtime and the substrate surface is damaged, for example.

Up to now, with a view to solving the above problem of theprecipitation/aggregation of the abrasive slurry, there have adoptedsuch treatment as redispersion treatment in which the abrasive slurry isstirred just before the use to redisperse the abrasive fine particles orseparation/removal treatment in which abnormal aggregate-particleshaving a particle size larger than a predetermined size as a result ofaggregation, are filtered, and separated and removed therefrom. Such thetreatments place a heavy burden on the leveling process for thesubstrate or the like.

Here, up to now, some proposals have been also made for solving theabove problem of the precipitation/aggregation of the abrasive slurry.

That is, a cerium oxide abrasive has been proposed (see JP 2000-17,195A). The cerium oxide abrasive contains cerium oxide fine particles, anammonium acrylate-methyl acrylate copolymer, and water and hardlyprecipitates, and can polish a surface to be polished of an SiO₂insulating film or the like at high speed without any damage.

Also, another cerium oxide abrasive has been proposed (see JP2001-138,214 A). The cerium oxide abrasive contains at least onecompound selected from the group consisting of a water-soluble organicpolymer, a water-soluble anionic surfactant, a water-soluble nonionicsurfactant, and a water-soluble amine as a dispersant. The abrasiveinvolves less precipitation with a maximum precipitation rate of 1 μm/sor less and enables the uniform dispersion with ease through stirring.The abrasive can polish a surface to be polished of an SiO₂ insulatingfilm or the like at high speed without any damage.

Further, another cerium oxide abrasive has been proposed (see JP2002-353,175 A). The cerium oxide abrasive contains: a firstpolyacrylate obtained by neutralizing more than 90% of the total ofcarboxyl groups in polyacrylic acid with ammonia; a second polyacrylateobtained by neutralizing 15 to 50% of the total of carboxyl groups inpolyacrylic acid with ammonia; and water. The total content of the firstpolyacrylate and the second polyacrylate in the abrasive is 0.15 to 1 wt%. The abrasive shows a high stability and causes neither two-layerseparation nor aggregation/precipitation/solidification, nor viscositychange.

However, those cerium oxide abrasives containing the dispersant arehardly kept in a sufficiently redispersed condition over 1 month orlonger while causing no precipitation/aggregation for such a long term.Also, in the manufacturing process, there is a case where a pipe of anapparatus is clogged with the aggregated abrasive or the like. Withthose abrasives, such problems are not always solved completely and theproblems still remain to be solved.

Also, those cerium oxide abrasives each contain a relatively largeamount (0.1 to 5 wt %) of organic compound such as the water-solubleorganic polymer, the water-soluble anionic surfactant, the water-solublenonionic surfactant, and the water-soluble amine as the dispersant. Awaste liquid after polishing contains inorganic substances constitutingthe cerium oxide particles and organic substances constituting thedispersant in a mixed form. As a result, a problem arises in that wasteliquid disposal requires a great deal of time and effort, and cost.

In addition, in view of reducing costs for producing or transporting theabrasive slurry as much as possible, it is desirable that the slurry beproduced at as high a concentration as possible during the production,and diluted to a given concentration when in use. The higher theconcentration, the more easily the precipitation/aggregation occurs.Therefore, there is a demand for development of the abrasive slurryhaving much superior dispersion stability.

SUMMARY OF THE INVENTION

In view of the above, the inventors of the present invention have madeextensive studies on an abrasive slurry keeping high dispersionstability for a long time and showing a satisfactory redispersionproperty, which can eliminate a problem about precipitation/aggregationas much as possible and can be used as a dispersant-free abrasivecontaining absolutely no organic dispersant. As a result, the inventorsof the present invention have found that the addition of colloidal fineparticles suppresses the precipitation/aggregation of the abrasive fineparticles as much as possible. The colloidal fine particles includecolloidal oxides and have an average particle size smaller than that ofthe abrasive fine particles. Thus, the present invention has beencompleted.

Accordingly, an object of the present invention is to provide anabrasive slurry keeping high dispersion stability for a long time andshowing a satisfactory redispersion property, which can eliminate aproblem about precipitation/aggregation as much as possible and can beused as a dispersant-free abrasive containing absolutely no organicdispersant.

Another object of the present invention is to provide a manufacturingmethod for a substrate. The method is utilized for manufacturing asubstrate such as a silicon substrate used in a semiconductormanufacturing process or an aluminum substrate used in an electrostaticchuck manufacturing process through CMP using the abrasive slurry withindustrial advantage.

More specifically, the present invention provides an abrasive slurryhaving high dispersion stability, including: abrasive fine particlesmade of one or more kinds of oxides; colloidal fine particles made ofcolloidal oxide with an average particle size smaller than an averageparticle size of the abrasive fine particles; and a dispersion medium inwhich the abrasive fine particles and the colloidal fine particles aredispersed.

Also, the present invention provides a manufacturing method for asubstrate as an inorganic substrate, including a step for polishing thesubstrate by using the abrasive slurry.

In the present invention, as the oxides used as the abrasive fineparticles, oxides conventionally used as the abrasive fine particles ofthis type maybe adopted with no modification. Specific examples thereofinclude: metal oxides such as cerium oxide (CeO₂) and manganese dioxide(MnO₂); silicon oxides (SiO₂) such as a precipitated silica, a fumedsilica, and a colloidal silica; aluminum oxides (Al₂O₃) such as a fumedalumina and a colloidal alumina. Those may be used singly or as amixture of two or more.

Among those oxides, preferably used as the abrasive fine particles inthe present invention are the cerium oxide fine particles and thealuminum oxide fine particles, for example, which have a relativelylarge specific gravity or average particle size and easilyprecipitate/aggregate by themselves. Those are effectively appliedparticularly to the abrasive fine particles.

An average particle size (Dp) of the abrasive fine particles used in thepresent invention is not particularly limited to a specific value andvaries depending on the kind thereof. In the case of the cerium oxideparticles, the size is generally 100 to 5,000 nm, preferably 500 to2,000 nm. Some kinds of abrasive fine particles cannot exert a polishingability sufficiently with the average particle size (Dp) below 100 nm.On the other hand, with the size above 5,000 nm, the surface to bepolished is easily damaged.

Further, the colloidal fine particles used together with the abrasivefine particles may be colloidal oxides such as a colloidal silica and acolloidal alumina, for example. Those can be used singly or as a mixtureof two or more.

An average particle size (Dc) of the colloidal fine particles should beat least smaller than the above size of the abrasive fine particles.Although varying depending on the kind thereof, in many cases includingthe case of using the colloidal silica, the average particle size isgenerally 10 to 300 nm, preferably 20 to 200 nm. A particle size ratio(Dc/Dp) of the average particle size (Dc) of the colloidal fineparticles to the average particle size (Dp) of the above abrasive fineparticles is 10 or less, preferably about 0.01 to 3. If the averageparticle size (Dc) of the colloidal fine particles is smaller than 10nm, the particles are unstable and the abrasive easily gelates duringthe production, whereas if the size is larger than 300 nm, the particlesize variation is likely to occur. In addition, the particle size ratio(Dc/Dp) is above 10, which results in too small abrasive fine particles.As a result, the polishing ability cannot be exerted sufficiently.

Furthermore, as a dispersion medium constituting the abrasive slurry, adispersion conventionally used in the abrasive slurry of this type maybe used with no modification. The medium is not particularly limited tospecific one but may be selected appropriately according to applicationsof the abrasive slurry, the applications including: an abrasive slurryfor CMP used for leveling a substrate such as a silicon substrate usedin a semiconductor manufacturing process or an aluminum substrate usedin an electrostatic chuck manufacturing process; an abrasive slurry forCMP used for polishing a surface to be polished of photomask blanks, aglass disk, an optical lens, or the like; and other generally-knownabrasive slurry used for polishing a surface to be polished. However,preferably used is water or an aqueous dispersion medium. The aqueousdispersion medium contains water as a main ingredient, and awater-soluble solvent. Examples of the water-soluble solvent include:alcohols such as methanol, ethanol, n-propanol, iso-propanol, n-butanol,and tert-butanol; ketones; esters; and ethers. In the dispersion medium,as in the conventional case, an etchant is added for chemical polishingin CMP if necessary.

A particle concentration (Cp) of the above abrasive fine particles inthe abrasive slurry of the present invention, although varying dependingon the kind of the abrasive fine particles, is generally 5 to 40 wt %,preferably 5 to 30 wt %, more preferably 5 to 10 wt % in the case of thecerium oxide particles. In addition, a particle concentration (Cc) ofthe colloidal fine particles in the slurry is generally 0.01 to 7.5 wt%, preferably 0.015 to 6.25 wt % in many cases including the case ofusing the colloidal silica. Further, a weight distribution ratio (Cc/Cp)of the colloidal fine particle concentration (Cc) to the abrasive fineparticle concentration (Cp) is 0.002 to 1.5, preferably 0.003 to 1.25.The abrasive slurry prepared at the particle concentrations (Cp) and(Cc) are used for polishing such as CMP without changing the initialparticle concentrations (Cp) and (Cc) or after being diluted to givenparticle concentrations (Cp) and (Cc). If the particle concentration(Cp) of the abrasive fine particles is less than 5 wt %, the polishingability is insufficient. In contrast, if the concentration is more than40 wt %, a dispersion stability is reduced. Also, with the particleconcentration (Cc) of the colloidal fine particles below 0.01 wt %, aneffect of suppressing the precipitation/aggregation is reduced, whereaswith the concentration (Cc) above 7.5 wt %, the aggregation phenomenonis likely to occur. Also if the weight distribution ratio (Cc/Cp) of thecolloidal fine particle concentration (Cc) to the abrasive fine particleconcentration (Cp) is less than 0.002, an effect of suppressing theprecipitation/aggregation is reduced in some cases. In contrast, if theweight distribution ratio (Cc/Cp) is above 1.5, the aggregationphenomenon is likely to occur.

The abrasive slurry according to the present invention keeps highdispersion stability for a long time even if the organic dispersant suchas the water-soluble organic polymer, the water-soluble anionicsurfactant, the water-soluble nonionic surfactant, or the water-solubleamine is not particularly added thereinto. Further, the slurry has asatisfactory redispersion property and can eliminate the problem aboutthe precipitation/aggregation as much as possible.

Also, in the present invention, any method of preparing the abrasiveslurry may be adopted with no particular limitation as far as theabrasive fine particles, the colloidal fine particles, and thedispersion medium constituting the slurry are uniformly mixed and theslurry is prepared in which the abrasive fine particles and thecolloidal fine particles are uniformly dispersed into the dispersionmedium. The slurry can be prepared by using a general stirrer andoptionally, a wet disperser such as an ultrasonic disperser, ahomogenizer, a ball mill, a vibrating ball mill, a planetary ball mill,or a medium stirring type mill.

The abrasive slurry of the present invention is used for leveling thesubstrate such as the silicon substrate used in the semiconductormanufacturing process or the aluminum substrate used in theelectrostatic chuck manufacturing process. In addition, the slurry isused for polishing: an oxide film such as a silicon oxide insulatingfilm formed on a wiring board having predetermined wirings; an inorganicinsulating film made of glass, silicon nitride, or the like; opticalglass for a photomask, a lens, a prism, or the like; an inorganicconductive film made of ITO or the like; an optical integrated circuit,an optical switching element, and an optical waveguide constituted ofglass and a crystalline material; an optical fiber end surface; anoptical single crystal such as a scintillator; a solid-laser singlecrystal; a blue laser LED sapphire substrate; a semiconductor singlecrystal such as SiC, GaP, or GaAs; a glass substrate for a magneticdisk; or a magnetic head, for example.

For example, consider a case of conducting CMP on a half-manufacturedsemiconductor substrate on which a circuit element and an aluminumwiring are formed or a semiconductor substrate prepared by furtherforming an oxide film such as a silicon oxide insulating film on theabove half-manufactured substrate, for leveling the oxide film surfaceto smooth out the unevennesses thereof. In this case, a generalpolishing apparatus equipped with a holder for holding the substrate anda rotating table attached with a polishing pad is used. The abrasiveslurry of the present invention is supplied successively to thepolishing pad in a given amount at a time by means of a pump etc., andthus the surface can be polished at a given rotation speed under a givenpressure.

The polished substrate is well washed in running water as in the generalpost-treatment, after which water droplets on the substrate are wipedoff and the substrate is dried with a spin drier or the like.

The waste liquid discarded at the time of polishing the substrate is adispersant-free liquid containing absolutely no organic dispersant, sothat the waste liquid disposal can be performed much more economicallythan before.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a preferred embodiment of the present invention will bedescribed in detail based on examples and comparative examples.

EXAMPLES 1 to 27

[Preparation of Colloidal Silica (20 nm)]

In a 1 m³-tank with jacket provided with a liquid distillation port, aliquid level controlling apparatus, and a stirrer, 32 kg ofmethylsilicate, 100 kg of methanol, and 768 kg of pure water werecharged and mixed to prepare a liquid A.

Also, in a 3 m³-tank provided with a stirrer, 368 kg of methylsilicate,100 kg of methanol, 1,840 g of pure water, and 12 kg of 28 wt %-ammoniawater were charged and mixed to prepare a liquid B.

Next, the tank containing the liquid A was steam-heated to distill off amixture liquid of methanol and water. At the time when the mixtureliquid began to distill off of the liquid A, the liquid B was added tokeep the liquid level of the liquid A at a predetermined level. Afterthe liquid B was completely added thereinto, 240 kg of pure water wasfurther added to keep the liquid level of the liquid A at thepredetermined level, followed by the reaction.

After the reaction, a reaction product was taken out of the tank inwhich the liquid A was charged and analyzed. As a result, the productwas a colloidal silica product (colloidal silica (20 nm)) having asilica content of 20 wt % and an average particle size of 20 nm.

[Preparation of Colloidal Silica (70 nm)]

In a 3 m³-tank with jacket provided with a stirrer, 1,721.7 kg ofmethanol, 306.3 kg of pure water, and 88.4 kg of 28 wt %-ammonia waterwere charged and mixed. After that, a liquid temperature was adjusted to23±1 C.°. While keeping the liquid temperature at 23±1 C.°, 404.4 kg ofmethylsilicate was added in 2 to 2.5 hours with stirring, followed bythe reaction.

After the reaction, a crude product of the resultant reaction mixturewas transferred to a 1 m³-tank with jacket provided with a liquiddistillation port, a liquid level controlling apparatus, and a stirrer,and the tank was steam-heated to distill off a mixture liquid ofmethanol, water, and ammonia. At the time when the mixture liquid beganto distill off of the tank, the remaining reaction mixture was added tokeep the liquid level at a predetermined level. After the reactionmixture was wholly added thereinto, pure water was further added to keepthe liquid level at the predetermined level until the liquid temperaturein the tank reached 100 C.°.

When the liquid temperature reached 100 C.°, heating was terminated tothereby offer an intermediate product. The product was cooled until theliquid temperature dropped to 70 C.°. At that point, an appropriateamount of 28 wt %-ammonia water was added and further, stirred andmixed, taking the reaction product off of the tank.

The resultant reaction product was a colloidal silica product (colloidalsilica (70 nm)) having a silica content of 30 wt % and an averageparticle size of 70 nm.

[Preparation of Colloidal Silica (170 nm)]

In a 1.8 m³-tank with jacket provided with a stirrer, 885.1 kg ofmethanol, 63.1 g of pure water, and 113.25 kg of 28 wt %-ammonia waterwere charged and mixed. After that, a liquid temperature was adjusted to23±1 C.°. While keeping the liquid temperature at 23±1 C.°, 171.1 kg ofmethylsilicate was added in 3 hours with stirring, followed by thereaction.

After the reaction, a crude product of the resultant reaction mixturewas transferred to a 1 m³-tank with jacket provided with a liquiddistillation port, a liquid level controlling apparatus, and a stirrer,and the tank was steam-heated to distill off a mixture liquid ofmethanol, water, and ammonia. At the time when the mixture liquid beganto distill off of the tank, the remaining reaction mixture was added tokeep the liquid level at a predetermined level. After the reactionmixture was wholly added thereinto, pure water was further added to keepthe liquid level at the predetermined level until the liquid temperaturein the tank reached 100 C.°.

When the liquid temperature reached 100 C.°, heating was terminated tothereby offer an intermediate product. The product was cooled until theliquid temperature dropped to 70 C.°. At that point, an appropriateamount of 28 wt %-ammonia water was added and further, stirred andmixed, taking the reaction product off of the tank.

The resultant reaction product was a colloidal silica product (colloidalsilica (170 nm)) having a silica content of 22 wt % and an averageparticle size of 170 nm.

[Preparation of Abrasive Slurry]

Cerium oxide particles (trade name: TE-508, produced by SEIMI CHEMICALCo., Ltd.) having an average particle size of 1.1 μm and a maximumparticle size of 8 μm were used as the abrasive fine particles. Thethree types of colloidal silica prepared above were used as thecolloidal fine particles. The pure water was used as the dispersionmedium. Those were mixed at a blending ratio shown in Table 1 anduniformly mixed by a stirrer, preparing abrasive slurry according toeach of Examples 1 to 27.

[Evaluation of Preparation/Aggregation Condition and RedispersionProperty]

An aliquot (50 ml) of the obtained abrasive slurry of each of Examples 1to 27 was put in a 100 ml-test tube and left standing for 1 month. Afterthat, a precipitation/aggregation condition thereof was visuallyobserved.

Also, 50 ml of abrasive slurry was put in a 100ml-polyethylene vesseland left standing for 1 month. Thereafter, a redispersion propertythereof was visually observed while shaking the vessel with hands. Inaddition, the vessel was laid and placed on a table ball mill stirrer(model: V-1M, manufactured by IRIE SHOKAI Co., Ltd.), followed bystirring under the stirring conditions of a rotation speed of 100 rpmand a time period of 10 minutes. Thus, the redispersion property withthe stirrer was visually observed.

The precipitation/aggregation condition and the redispersion propertywere evaluated based on the following four criteria.

-   -   ⊚: The whole precipitated portion was soft, which could be        redispersed through shaking with hands for several seconds and        redispersed through stirring with the stirrer for 5 or less        minutes.    -   ◯: The precipitated portion was partially solidified, which took        about 30 seconds to redisperse through shaking with hands and        about 10 minutes to redisperse through stirring with the        stirrer.    -   Δ: The precipitated portion was partially solidified, which took        2 or more minutes to redisperse through shaking with hands and        about 10 minutes to redisperse through stirring with the        stirrer.    -   ×: The whole precipitated portion was solidified throughout,        which could not be redispersed even through shaking with hands        for 10 minutes and which took 10 or more minutes to redisperse        through stirring with the stirrer.

The results are shown in Table 1.

[Quartz Substrate Polishing Rate]

Further, the abrasive slurry was diluted three-fold with ultrapurewater. A CMP polishing apparatus with a polishing pad (FACT-200,manufactured by Nanofactor K.K.) was used to polish a sample (quartzsubstrate measuring 3.3 cm×2.6 cm in width and length with a thicknessof 1.15 mm) for 10 minutes under the conditions that the rotation speedwas 200 rpm, a process pressure was 500 g/cm², and a supply rate of theabrasive slurry was 10 ml/min. The thickness of the sample was measuredwith a micrometer before and after polishing, and a difference of thethickness between before and after polishing was obtained forcalculating a polishing rate (μm/10 min) with respect to the quartzsubstrate (SiO₂).

The results are shown in Table 1.

COMPARATIVE EXAMPLES 1 to 15

As an organic dispersant, polyvinyl pyrrolidone (PVA) was used.Similarly to Examples 1 to 27 above, abrasive slurry of each ofComparative Examples 1 to 15 was prepared. The prepared abrasive slurryof each of Comparative Examples 1 to 15 was evaluated for theprecipitation/aggregation condition and the redispersion property in thesame way as in Examples 1 to 27 above. Further, the polishing rate(μm/10 min) with respect to the quartz substrate (SiO₂) was calculated.

The results are shown in Table 1 together with those of Examples 1 to 27above. TABLE 1 Example No. 1 2 3 4 5 6 7 8 9 COA CeO₂ (Cc) 5 15 30 5 1530 5 15 30 wt % Co—SiO₂(20 nm) (Cp) 1 1 1 2 2 2 5 5 5 Cc/Cp 0.2 0.070.03 0.4 0.13 0.07 1.0 0.33 0.17 Dispersant — — — — — — — — — Dispersionstability ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ Polishing ability 10 10 10 10 10 10 10 10 10Example No. 10 11 12 13 14 15 16 17 18 COA CeO₂ (Cc) 5 15 30 5 15 30 515 30 wt % Co—SiO₂(70 nm) (Cp) 1 1 1 2 2 2 5 5 5 Cc/Cp 0.2 0.07 0.03 0.40.13 0.07 1 0.33 0.17 Dispersant — — — — — — — — — Dispersion stability⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ Polishing ability 10 10 10 10 10 10 10 10 10 ExampleNo. 19 20 21 22 23 24 25 26 27 COA CeO₂ (Cc) 5 15 30 5 15 30 5 15 30 wt% Co—SiO₂(170 nm) (Cp) 1 1 1 2 2 2 5 5 5 Cc/Cp 0.2 0.07 0.03 0.4 0.130.07 1.0 0.33 0.17 Dispersant — — — — — — — — — Dispersion stability ⊚ ⊚⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ Polishing ability 10 10 10 10 10 10 10 10 10 ComparativeExample No. 1 2 3 4 5 6 7 8 9 COA CeO₂ (Cc) 5 15 30 5 15 30 5 15 30 wt %Co—SiO₂ (Cp) — — — — — — — — — Cc/Cp — — — — — — — — — Dispersant — — —1 1 1 3 3 3 Dispersion stability X X X Δ Δ Δ X X X Polishing ability — —— 10 10 10 10 10 10 Comparative Example No. 10 11 12 13 14 15 COA CeO₂(Cc) 5 15 30 5 15 30 wt % Co—SiO₂ (Cp) — — — — — — Cc/Cp — — — — — —Dispersant 1 1 1 3 3 3 Dispersion stability Δ Δ Δ ◯ Δ Δ Polishingability 10 10 10 10 10 10(Note)COA wt %: Composition of abrasive (wt %)CeO₂: Cerium oxide particleCo—SiO₂: Colloidal silicaDispersion stability: Evaluation of precipitation/aggregation conditionand redispersion propertyPolishingability: Quartzsubstratepolishingrate(three-folddiluent: μm/10min)

COMPARATIVE EXAMPLES 16 to 21

The abrasive slurry having the composition as shown in Table 2 accordingto each of Comparative examples 16 to 21 were prepared by using the samecerium oxide particles and three types of colloidal silica as used inthe above-mentioned Examples 1 to 27 in the same manner as described inthe above-mentioned Examples. To the abrasive slurry according to eachof Comparative Examples 16 to 21, the preparation/aggregation conditionand redispersion property were evaluated by the same way as described inthe above-mentioned Examples, and the quartz substrate polishing ratewas also measured by the same way as described in the above-mentionedExamples. The results are shown in Table 2. TABLE 2 Comparative exampleNo. 16 17 COA CeO₂ (Cc) 5 5 wt % Co—SiO₂(20 nm) (Cp) 10 15 Cc/Cp 2.0 3.0Dispersant — — Dispersion stability X X Polishing ability 7 5Comparative example No. 18 19 COA CeO₂ (Cc) 5 5 wt % Co—SiO₂(70 nm) (Cp)10 15 Cc/Cp 2.0 3.0 Dispersant — — Dispersion stability X X Polishingability 7 5 Comparative example No. 20 21 COA CeO₂ (Cc) 5 5 wt %Co—SiO₂(170 nm) (Cp) 10 15 Cc/Cp 2.0 3.0 Dispersant — — Dispersionstability X X Polishing ability 7 5(Note)COA wt %, CeO₂, Co—SiO₂, Dispersion stability, and Polishing ability arethe same meaning as described in Table 1.

As apparent from the results shown in Table 1, the abrasive slurryaccording to each of Examples 1 to 27 of the present invention exertedexcellent properties in terms of the evaluation on theprecipitation/aggregation condition and the redispersion property andthe quartz substrate polishing rate. In contrast, the abrasive slurry ofeach of Comparative Examples 1 to 3, which was added with neither thecolloidal fine particles nor the dispersant, could not be redispersedand the polishing rate thereof could not be measured. The abrasiveslurry of each of Comparative Examples 4 to 15, which was added onlywith 1 wt % to 3 wt % of dispersant, took much time to redisperse.Moreover, the abrasive slurry of each of Comparative Examples 16 to 21described in Table 2, which had 2.0 or 3.0 of Cc/Cp, were clearlyinferior in the evaluation on the precipitation/aggregation conditionand the redispersion property and remarkably slower in the quartzsubstrate polishing rate than the abrasive slurry according to each ofExamples 1 to 27 of the present invention. The results revealed that theabrasive slurry according to the present invention could have thesuperior property particularly in terms of the precipitation/aggregationcondition and the redispersion property.

EXAMPLES 28 TO 48 AND COMPARATIVE EXAMPLES 22 TO 24

The abrasive slurry having the composition as shown in Table 3 accordingto each of Examples 28 to 48 and Comparative examples 22 to 24 wereprepared by using the same cerium oxide particles and three types ofcolloidal silica as used in the above-mentioned Examples in the samemanner as described in the above-mentioned Examples.

The precipitation/aggregation condition and the redispersion propertywere evaluated in the same manner as described in the above-mentionedExamples.

The results are shown in Table 3. TABLE 3 Example No. Co-ex. 28 29 30 3132 33 34 22 COA CeO₂ (Cc) 5 5 5 5 5 5 5 5 wt % Co—SiO₂(20 nm) (Cp) 0.010.015 0.025 0.05 0.5 6.25 7.5 8.25 Cc/Cp 0.002 0.003 0.005 0.01 0.1 1.251.5 1.65 Dispersion stability Δ ⊚ ⊚ ⊚ ⊚ ⊚ Δ X Example No. Co-ex. 35 3637 38 39 40 41 23 COA CeO₂ (Cc) 5 5 5 5 5 5 5 5 wt % Co—SiO₂(70 nm) (Cp)0.01 0.015 0.025 0.05 0.5 6.25 7.5 8.25 Cc/Cp 0.002 0.003 0.005 0.01 0.11.25 1.5 1.65 Dispersion stability Δ ⊚ ⊚ ⊚ ⊚ ⊚ Δ X Example No. Co-ex. 4243 44 45 46 47 48 24 COA CeO₂ (Cc) 5 5 5 5 5 5 5 5 wt % Co—SiO₂(170 nm)(Cp) 0.01 0.015 0.025 0.05 0.5 6.25 7.5 8.25 Cc/Cp 0.002 0.003 0.0050.01 0.1 1.25 1.5 1.65 Dispersion stability Δ ⊚ ⊚ ⊚ ⊚ ⊚ Δ X(Note)COA wt %, CeO₂, Co—SiO₂, and Dispersion stability are the same meaningas described in Table 1 and Co-ex. is the meaning of Comparativeexample.

As apparent from the result shown in Table 3, the abrasive slurry having0.002 to 1.5 according to each of Examples 28 to 34, 35 to 41 and 42 to48, especially 0.003 to 1.25 of Cc/Cp according to each of Examples 29to 33, 36 to 40 and 43 to 47, exhibited excellent result in theevaluation on the preparation/aggregation condition and the redispersionproperty.

As opposed to the abrasive slurry having 1.65 of Cc/Cp, according to theabove-mentioned comparative examples 22 to 24, was not satisfied withthe preparation/aggregation condition and the redispersion property.

According to the present invention, it is possible to provide theabrasive slurry keeping high dispersion stability for a long time andshowing a satisfactory redispersion property, which can eliminate aproblem about precipitation/aggregation as much as possible and can beused as a dispersant-free abrasive containing absolutely no organicdispersant.

Also, the abrasive slurry of the present invention is used, whereby itis possible to manufacture the substrate such as the silicon substrateused in the semiconductor manufacturing process or the aluminumsubstrate used in the electrostatic chuck manufacturing process throughCMP with industrial advantage.

1. An abrasive slurry having high dispersion stability, consisting of:abrasive fine particles made of one or more kinds of oxides; colloidalfine particles made of colloidal oxide with an average particle sizesmaller than an average particle size of the abrasive fine particles;and a dispersion medium in which the abrasive fine particles and thecolloidal fine particles are dispersed; wherein the average particlesize (Dp) of the abrasive fine particles is 100 to 5,000 nm, the averageparticle size (Dc) of the colloidal fine particles is 10 to 300 nm, anda particle size ratio (Dc/Dp) of the average particle size (Dc) of thecolloidal fine particles to the average particle size (Dp) of theabrasive fine particles is 10 or less, and the abrasive fine particleshave a particle concentration (Cp) of 5 to 30 wt %, the colloidal fineparticles have a particle concentration (Cc) of 0.01 to 7.5 wt %, and aweight distribution ratio (Cc/Cp) of the particle concentration (Cc) ofthe colloidal fine particles to the particle concentration (Cp) of theabrasive fine particles is 0.002 to 1.5.
 2. The abrasive slurry havinghigh dispersion stability according to claim 1, wherein the dispersionmedium comprises water or an aqueous dispersion medium mainly containingwater.
 3. The abrasive slurry having high dispersion stability accordingto claim 1, wherein the abrasive fine particles comprise a cerium oxideparticle.
 4. The abrasive slurry having high dispersion stabilityaccording to claim 1, wherein the colloidal fine particles comprise acolloidal silica.
 5. The abrasive slurry having high dispersionstability according to any one of claim 1, wherein the colloidal fineparticles have the particle concentration (Cc) of 0.015 to 6.25 wt %,and a weight distribution ratio (Cc/Cp) of the particle concentration(Cc) of the colloidal fine particles to the particle concentration (Cp)of the abrasive fine particles is 0.003 to 1.25.
 6. The abrasive slurryhaving high dispersion stability according to any one of claims 1 to 5,wherein no organic dispersant is contained therein.
 7. A manufacturingmethod for a substrate as an inorganic substrate, comprising polishingthe substrate using the abrasive slurry according to any one of claim 1.8. The manufacturing method for a substrate according to claim 7,wherein the substrate has a surface on which an oxide film is formed. 9.A manufacturing method for a substrate as an inorganic substrate,comprising polishing the substrate using the abrasive slurry accordingto claim 6.